One known valve timing control device for an internal combustion engine is described in the after-mentioned Patent Document-1.
The known device will be briefly described in the following. The device comprises a housing member that receives a torque from a crankshaft and has therein a plurality of operation oil chambers extending around an inner cylindrical surface of the housing, a front plate that includes a plate part closing at its rear surface a front open part of the housing member and a cylindrical part formed on a central portion of a front surface (outer end surface) of the plate part, a vane rotor that is received in the housing member and rotatable in a given range in both the most delayed angle side and most advanced angle side relative to the housing member and has four vanes for grouping the operation oil chambers into delayed angle operation oil chambers and advanced angle operation oil chambers, and a torsion spring that is partially received in the cylindrical part of the front plate and has one end engaged to a front edge of the cylindrical part and the other end engaged to the vane rotor.
The torsion spring is arranged to bias the vane rotor in the advanced angle side by its biasing force, and by controlling the open/close timing of the exhaust valves in the advanced angle side for improving the engine startability.